/**
 * https://leetcode.cn/problems/binary-tree-pruning/
 * Definition for a binary tree node.
 * public class TreeNode {
 * int val;
 * TreeNode left;
 * TreeNode right;
 * TreeNode() {}
 * TreeNode(int val) { this.val = val; }
 * TreeNode(int val, TreeNode left, TreeNode right) {
 * this.val = val;
 * this.left = left;
 * this.right = right;
 * }
 * }
 */
class Solution {
    public TreeNode pruneTree(TreeNode root) {
        if (root == null)
            return root;

        root.left = pruneTree(root.left);
        root.right = pruneTree(root.right);

        if (root.left == null && root.right == null && root.val == 0)
            root = null;
        return root;
    }
}